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1. Visual AttentionVisual Attention
Cognitive overview of the problemCognitive overview of the problem
of attentionof attention
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2. What is Attention?What is Attention?
““Everybody knows what attention is. It is takingEverybody knows what attention is. It is taking
possession by the mind, in clear and vivid form,possession by the mind, in clear and vivid form,
of one out of what seem several simultaneouslyof one out of what seem several simultaneously
possible objects or trains of thought.possible objects or trains of thought.
Focalization, concentration of consciousness areFocalization, concentration of consciousness are
of its essence. It implies withdrawal from someof its essence. It implies withdrawal from some
things in order to deal effectively with others ,things in order to deal effectively with others ,
and is a condition which has a real opposite inand is a condition which has a real opposite in
the confused, dazed scatterbrain state … “the confused, dazed scatterbrain state … “
William James (1890)William James (1890)
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3. What is Attention?What is Attention?
 ‘‘Taking possession of the mindTaking possession of the mind’’
– Controlling the focus of attention; intentionality; “Please payControlling the focus of attention; intentionality; “Please pay
attention …”attention …”
 ‘‘one out of what seem several simultaneously possibleone out of what seem several simultaneously possible
objectsobjects’’
– Our apparent inability to attend to multiple things at onceOur apparent inability to attend to multiple things at once
 ‘‘It implies withdrawal from some things in order to dealIt implies withdrawal from some things in order to deal
effectively with otherseffectively with others’’
– Attending has a costAttending has a cost
– Attending is a limited capacity processAttending is a limited capacity process
 ‘‘has a real opposite in the confused, dazed scatterbrainhas a real opposite in the confused, dazed scatterbrain
statestate’’
– Attending is the glue that keeps perception togetherAttending is the glue that keeps perception together
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4. AttentionAttention: S: Selecting some stimulielecting some stimuli
over others for further processingover others for further processing
 Why select? Why not process all visual input?Why select? Why not process all visual input?
– Limited processing capacityLimited processing capacity
 Limited processing capacity of what?Limited processing capacity of what?
– Response systems: Two hands, one mouth, etc.Response systems: Two hands, one mouth, etc.
– Input: One pair of foveasInput: One pair of foveas
– Use of distributed representations: When more thanUse of distributed representations: When more than
one pattern is activated simultaneously, interferenceone pattern is activated simultaneously, interference
or cross-talk may occur.or cross-talk may occur.
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5. Coping with the problem ofCoping with the problem of
interference and cross talkinterference and cross talk
 Reducing the degree of distributedness atReducing the degree of distributedness at
higher levels of visual representationhigher levels of visual representation
 Evidence of sparse population codes (e.g., IT faceEvidence of sparse population codes (e.g., IT face
representations)representations)
 Binding attributes via synchronized oscillationsBinding attributes via synchronized oscillations
 Selective Attention: Focusing processingSelective Attention: Focusing processing
on a selected portion of the sceneon a selected portion of the scene
 Reduces information overloadReduces information overload
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6. Selective AttentionSelective Attention
 Selective attention: Limits the processingSelective attention: Limits the processing
to one portion of the scene at a time.to one portion of the scene at a time.
 Stimulus selection could be based on:Stimulus selection could be based on:
– location in a (retinotopic map)location in a (retinotopic map)
– object representationobject representation
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7. Spatial-based SelectionSpatial-based Selection
 Posner’s Spatial CuingPosner’s Spatial Cuing
Procedure.Procedure.
- See fixation cross- See fixation cross
- Brightness change- Brightness change
- Respond to target onset- Respond to target onset
 Fastest response to aFastest response to a
target that occurs on thetarget that occurs on the
cued side (valid) andcued side (valid) and
slowest when targetslowest when target
occurs on the non-cuedoccurs on the non-cued
side (invalid).side (invalid).
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8. Object-based SelectionObject-based Selection
 TaskTask
– Told what dimension(s) to reportTold what dimension(s) to report
– Fixation pointFixation point
– See target (~79 ms)See target (~79 ms)
– Pattern maskPattern mask
– ReportReport
 Target: Two overlapping objects, each with 2Target: Two overlapping objects, each with 2
dimensions:dimensions:
– Box: Height; GapBox: Height; Gap
– Line: Texture; OrientationLine: Texture; Orientation
 Equally accurate reporting one or two dimensionsEqually accurate reporting one or two dimensions
from the same objectfrom the same object
 More accurate reporting two dimensions from theMore accurate reporting two dimensions from the
same object than one dimension from each of twosame object than one dimension from each of two
objects. (Vecera & Farah, 1994, E1: 86% > 80%)objects. (Vecera & Farah, 1994, E1: 86% > 80%)
After Duncan (1980)
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9. Visual Attention:Visual Attention: The Glue that BindsThe Glue that Binds
 We normally experience our complex environments as a coherentWe normally experience our complex environments as a coherent
world of integrated objects.world of integrated objects.
 Remember: Sensory information (i.e., shape, color, motion) arrivesRemember: Sensory information (i.e., shape, color, motion) arrives
in parallel and is processed by different pathways in brain.in parallel and is processed by different pathways in brain.
 To create useful mental representations of objects, we collect theirTo create useful mental representations of objects, we collect their
features, bind them into the correct temporal and spatial bundles,features, bind them into the correct temporal and spatial bundles,
and interpret these bundles to specify their real world origins.and interpret these bundles to specify their real world origins.
 This process depends upon focused attention.This process depends upon focused attention.
 If focused attention fails, binding may fail and we perceive illusoryIf focused attention fails, binding may fail and we perceive illusory
conjunctions (i.e., upon seeing two cars (red Focus and black Echo,conjunctions (i.e., upon seeing two cars (red Focus and black Echo,
may falsely report a red Echo).may falsely report a red Echo).
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10. Feature Integration Theory:Feature Integration Theory:
Treisman (1998)Treisman (1998)
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11. Limited Visual InputLimited Visual Input
 Although we seem to have a detailed,Although we seem to have a detailed,
highly veridical and continuous mentalhighly veridical and continuous mental
representation of visual world about us,representation of visual world about us,
visual input is limited.visual input is limited.
– Visual acuity is good only for foveal focus.Visual acuity is good only for foveal focus.
– Eyes movement from one fixation point toEyes movement from one fixation point to
another while viewing a scene.another while viewing a scene.
 Saccades: 3-5 saccades/sec, 40 – 50 msec each.Saccades: 3-5 saccades/sec, 40 – 50 msec each.
 Fixations: ~300 msec, during which we pick upFixations: ~300 msec, during which we pick up
visual information.visual information.
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12. Eye Movements:Eye Movements: Saccades and FixationsSaccades and Fixations
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13. Change BlindnessChange Blindness
 Failure to detect supraliminal changes in a visualFailure to detect supraliminal changes in a visual
scene. (i.e., editing discontinuities in movies).scene. (i.e., editing discontinuities in movies).
 Flicker technique: In your demonstration,Flicker technique: In your demonstration,
changes involved: color, size, location,changes involved: color, size, location,
presence/absence of objects in scene.presence/absence of objects in scene.
Winter 2006 data (Psych 3450)Winter 2006 data (Psych 3450)
AccuracyAccuracy LatencyLatency
Central InterestCentral Interest 96%96% 5.5 sec5.5 sec
Marginal Interest 84%Marginal Interest 84% 13.5 sec13.5 sec
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14. Two Empirical Issues to be AddressedTwo Empirical Issues to be Addressed
from the Neuroscience Perspectivefrom the Neuroscience Perspective
1)1) How does attention affect visualHow does attention affect visual
information processing at differentinformation processing at different
stages?stages?
2)2) What neural systems control theWhat neural systems control the
allocation of attention?allocation of attention?
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